Conventionally, a composite substrate configured by bonding a plurality of substrates together has been used in inkjet heads and the like. In this type of composite substrate, protrusion-like bump parts are disposed between the bottom surface of the first substrate and the top surface of the second substrate, and the two substrates are bonded together through the bump parts.
The bump parts described above include two types of bump parts having substantially the same shape, and specifically a first bump part and a second bump part. The first bump part has bumps for forming electrically conductive connections. The first bump part is disposed so as to contact electrical contacts provided on the top surface of the second substrate to form electrical connections between the first substrate and second substrate. The second bump part is configured of an insulating material and is arranged in a position separated from the electrical contacts.